Cyclosporin A (CsA) and FK 506 are immunosuppressant natural substances derived from fungi which inhibit the Ca.sup.2+ -dependent signal transmission pathway in some cell types. In T cells, both agents inhibit the transcription of a number of genes, including the gene for IL-2, which is activated by stimulation of the T cell receptors (TCR). FK 506 and CsA both bind with high affinity to soluble receptor proteins (G. Fischer et al., Nature 337, 476-478, 1989, M. W. Harding et al., Nature 341, 755-760, 1989). The FK 506 receptor was called FKBP, the CsA receptor cyclophilin (Cyp). Both proteins catalyse the isomerization of cis- and trans-amide bond rotamers of peptides and are also frequently called immunophilins.
The supramolecule of CsA-Cyp or FK 506-FKBP binds calcineurin (CN) and inhibits its phosphatase activity. A cellular target molecule of CN was recognized as the cytosolic, phosphorylated component of the transcription factor NF-AT which, with inadequate CN activity for the action in the cell nucleus, cannot be dephosphorylated and thus the active transcription complex on the IL-2 promoter cannot be switched on (M. K. Rosen, S. L. Schreiber, Angew. Chem 104 (1992); 413-430; G. Fischer, Angew. Chem. 106 (1994), 1479-1501).
The allergic, asthmatic disorders are based on an inflammatory reaction which is controlled by T cells and their mediators. Corticosteroids are still the agent of choice in the treatment of many allergic disorders. CsA and FK 506 also proved in animal experiments and in clinical studies to be a favorable therapeutic in bronchial asthma and underlying inflammations. In animal experiments, it was possible to show the blockade of various cytokines such as IL-2, IL-4 and IL-5, which cause allergically induced inflammations. Despite the multiplicity of attempts at the identification of novel active immunophilin inhibitors, it was not possible until now to prepare or isolate any more efficacious structures than CsA, FK 506, rapamycin or derivatives of these natural substances. The high inhibitory potential of CsA, FK 506 or rapamycin, however, is very considerably reduced by the manifold side effects, in particular of the kidneys, and neurotoxicity (N. H. Sigal et al., J. Exp. Med. 173, 619-628, 1991). What lies behind this fact is the non-specificity of the interaction between immunophilin ligands and the cell-specific binding proteins. As a result, the known medicinal therapeutic action of these immunosuppressants is considerably restricted. Furthermore, the inadequate selectivity of the compounds proves problematical, particularly in long-term therapy.
A further compound having immunosuppressant properties was discovered during the screening of substance mixtures (G. Quinkert, H. Bang and D. Reichert, Helv. Chim. Acta 1996, 79, 1260). The structure published there is an indoline-2-carboxamide which at 10 .mu.mol exhibited an inhibition of IL-2 proliferation of 77% and at 1 .mu.mol an inhibition of IL-2 proliferation of 12%. New measurements at a concentration of 10 .mu.mol showed an IL-2-dependent inhibition of proliferation of 29%.
A substance class which likewise contains indolinecarboxylic acid as a central unit and exhibits immunosuppressant properties as well as antiasthmatic properties was described in German patent No. 1,961,6509.1.